Figure 9.

Model for TREX component recruitment to intronless and intron-containing genes. (A) Our data indicate that once the TREX complex is recruited to the site of transcription, presumably via the transcription machinery, the complex dissociates. The THO complex remains associated with the DNA or transcription machinery. Sub2p is immediately and efficiently transferred to the nascent RNA. The Yra1p divides into two pools: one remains associated with the DNA and the other is transferred to the RNA. (B) On intron-containing genes, the TREX complex is recruited normally but the transfer of Sub2p and Yra1p to the RNA may be hindered by the spliceosome. As a result, less Sub2p and Yra1p are retained at the site of transcription (S=Sub2p; Y=Yra1p).